Prediction of peripheral fracture risk by quantitative microdensitometry

The purpose of the study was to investigate whether quantitative microdensitometry (QMD) could be used for screening purposes to identify a population with a high risk for peripheral osteoporotic fractures.

In 1984 bone mineral density (BMD) measurements were made on the index finger of 612 women. Repeated BMD measurements were obtained in 1989 in 440 women. Cox proportional hazards models were used to obtain adjusted estimates of the hazard ratio of a fracture according to BMD or bone loss. Receiver operating characteristic curves were constructed and the areas under the curves (AUC) were compared.

Thirty-five women experienced peripheral osteoporotic fractures between the first and the second measurement. Women in the three lowest quartiles of bone density were 1.4-1.8 times (diaphyseal site) and 2.4-2.8 times (metaphyseal site) as likely to experience a fracture as those in the highest quartile. Women in the quartile with the highest bone loss had a risk of 6.9 (diaphyseal site) and 7.5 (metaphyseal site) times higher than women in the lowest quartile. The discriminative power of the measurement as a single test was moderate (AUC 63%); two successive measurements, made with an interval of 5 years to measure bone loss, increased the discriminating power (AUC 74%; P < 0.05).

Phalangeal BMD and bone loss, as measured by QMD, are important risk factors for peripheral osteoporotic fractures, but cannot be used as an efficient screening instrument for selecting women with the highest fracture risk.